1. Field of the Invention
The present invention relates to the field of semiconductor devices and, more particularly, to a method of forming a thin film of a semiconductor device using atomic layer deposition (ALD).
2. Description of the Related Art
Forming thin films in state-of-the-art highly integrated semiconductor devices requires many rigorous manufacturing requirements such as a low thermal budget, excellent step coverage, accurate control of film thickness, simple process variables, and low particulate contamination.
Conventional CVD-based methods such as low-pressure chemical vapor deposition (LPCVD), plasma-enhanced chemical vapor deposition (PECVD) are no longer adequate for forming thin films in state-of-the-art devices, meeting the manufacturing requirements. For example, in a typical CVD method, a thin film is deposited at a relatively high temperature. This is undesirable because of the possibility of adverse thermal effects on the devices. Also, the CVD thin film often has drawbacks such as a non-uniform thickness, i.e., thickness variations across the surface of the device or particulate contamination.
As for LPCVD, the hydrogen content of a LPCVD thin film is usually high, and step coverage thereof is often unacceptable.
The atomic layer deposition (ALD) process has been proposed as an alternative to such conventional thin film formation technologies because the ALD process can be performed at lower temperatures than conventional CVD-based methods and also exhibits excellent step coverage.
One such ALD process technology is disclosed in U.S. Pat. No. 6,124,158. Here, a first reactant is introduced to react with the treated surface to form a bonded monolayer of reactive species. A second reactant is introduced to react with the surface to form a desired thin film. After each step in the cycle, the reaction chamber is purged with an inert gas to prevent reaction except on the surface. Typically, the supplying of the reactant and the purging are implemented under the same pressure due to reasons such as the maintenance of fabrication equipment.
However, such conventional ALD technologies also have several drawbacks such as low throughput due to problems such as a relatively low growth rate of atomic layers. Further, the reaction space of conventional ALD reactors such as a traveling wave-type reactor is designed to be very small to reduce the purging volume for purging of byproducts or the like. Thus, conventional ALD reactors only process one or two wafers in each operation, typically one substrate for one operation in a single reactor. Such drawbacks have made it difficult for many conventional ALD technologies to be put in practical applications and commercially acceptable, i.e., mass production.
Recently, several attempts have been made to increase the throughput of the ALD process. One such attempt is disclosed in U.S. Pat. No. 6,042,652. Here, the ALD reactor includes a plurality of modules and a plurality of reaction spaces (stages), i.e., spaces partitioned with the plurality of assembled modules. For example, a lower module is placed below an upper module, thereby creating one reaction space (one stage) between them, which is capable of receiving merely one semiconductor substrate.
However, because each reaction space (stage) is small and partitioned, i.e. being separated from each other, each substrate is inserted in one of the reaction spaces (stages) one by one. Thus, it is hard to utilize an automated wafer transfer mechanism for loading/unloading of the plurality of wafers. Consequently, it takes a significantly long time to load/unload wafers. Also, the number of wafers that can be loaded and processed is still not sufficient.
Accordingly, what is clearly needed is a novel ALD process enabling high throughput that can deal with above mentioned problems while still providing high-quality thin films.
The present invention provides a method of forming a thin film using atomic layer deposition (ALD). A reactor having a single reaction space is provided. A batch of substrates is concurrently loaded into the single reaction space of the reactor.
Then, a gas containing reactants is introduced into the single reaction space, and a portion of the reactants is chemisorbed on top surfaces of the batch of substrates or wafers within the single reaction space. Non-chemically adsorbed reactants are then removed from the single reaction space.
In accordance with one embodiment of the present invention, after introducing the gas containing reactants, non-chemically adsorbed reactants are diluted in the single reaction space to facilitate the removal of non-chemically adsorbed reactants.
Also, according to another embodiment of the present invention, a method of forming a thin film is disclosed in which a reactor having a single reaction space is provided. A plurality of wafers, each having a processing surface, is introduced into the reaction space. The processing surfaces of the plurality of wafers face in substantially the same direction. First reactants are introduced into the reaction space such that a portion of the first reactants is chemically adsorbed on the processing surfaces of the plurality of wafers for ALD. Then, a non-chemically adsorbed portion of the first reactants is removed from the reaction space. Next, second reactants are introduced into the reaction space. Also, a portion of the second reactants is chemically adsorbed on the processing surface of each of the plurality of wafers. Subsequently, a non-chemically adsorbed portion of the second reactant is removed from the reaction space.
The foregoing and other objects, features and advantages of the invention will become more readily apparent from the following detailed description of a preferred embodiment of the invention that proceeds with reference to the accompanying drawings.